1. Field of the Invention
The present invention relates to a thin-film piezoelectric bimorph element, a mechanical detector and an inkjet head using the same, and methods of manufacturing the same.
2. Description of the Prior Art
In recent years, research and development has been conducted on a dielectric substance, in particular a ferroelectric substance, as a basic material of a pyroelectric IR detector using a pyroelectric property, a piezoelectric detector (sensor) and a piezoelectric actuator using a piezoelectric property, a nonvolatile memory using polarization inversion, a capacitive element using a high-dielectric-constant property, and the like.
The piezoelectric detector has been used as a mechanical detector for detecting a dynamic amount such as acceleration or pressure by using a “piezoelectric effect,” which is the generation of charge from a piezoelectric member as a result of the application of a force to the piezoelectric member. The piezoelectric detector features an eminently high sensitivity to voltage.
In contrast to the detector, the piezoelectric actuator provides a dynamic amount such as deformation by using a strain caused by the application of a voltage to a piezoelectric member. The piezoelectric actuator features excellent responsivity and the capability of precise control of an extremely small displacement.
If the piezoelectric detector or piezoelectric actuator is designed to have a bimorph structure in which a pair of piezoelectric members are bonded to the both surfaces of a metal plate which are in opposing relation to each other along the thickness thereof (piezoelectric bimorph element), the performance thereof can be improved significantly.
In a conventional piezoelectric bimorph element, a pair of piezoelectric members that have been subjected to a polarization process are bonded adhesively to the both surfaces of a metal plate which are in opposing relation to each other along the thickness thereof. However, since it is extremely difficult to uniformly control the thickness and hardening of an adhesive agent, the conventional piezoelectric bimorph element has the problem of sensitivity variations due to non-uniform adhesion.
Moreover, since one of the piezoelectric members provided on the both surfaces of the metal plate which are in opposing relation to each other along the thickness thereof contracts and the other expands, a high stress is produced at the adhesion interface. Over a prolonged period of use, the piezoelectric members may peel off the metal plate, which leads to the problem of insufficient durability.
Furthermore, the thickness of the piezoelectric members cannot be reduced excessively since a certain degree of rigidity is required by the piezoelectric members to adhere to the metal plate. This makes it difficult to fabricate a bimorph element using thin-film piezoelectric members (thin-film piezoelectric bimorph element).
Accordingly, it is impossible to scale down the conventional piezoelectric bimorph element and increase the performance thereof. It is therefore difficult to scale down a mechanical detector or an inkjet head using the element and improve the performance thereof.
The present invention has been achieved in view of the foregoing and it is therefore an object of the present invention to enable the manufacturing of a compact and high-performance thin-film piezoelectric bimorph element at low cost.